Evaporative cooling device for a centrifuge rotary seal

ABSTRACT

A device for cooling a rubbing seal interface between a stationary and a rotating surface. The device includes a hermetically sealed cooled container having thermally conductive walls partially filled with a volatile liquid with a face portion forming the stationary surface. In operation the heat generated at the interface causes the volatile liquid to evaporate and then condense by absorption of heat at the cooled container walls.

United States Patent 1 3,602,425

[72] Inventor William L. Schmidt 3,024,298 3/1962 Goltsos et a1. 62/ 1 l9 UX Menlo Park, Calll. 3,103,489 9/1963 Pickels 233/21 [21] Appl. No. 814.556 3,112,890 12/1963 Snelling 62/119 X [22] Filed Apr- 9, 1969 3,226,941 1/1966 Snelling 62/ l 19 UX [45] Patented Aug. 31, I971 Mm ry Examlner=lordun Franklin 1 Amgnee Assistant Examiner-George H. Krizmanich An0meyFlehr, l-lohbach, Test, Albritton and Herbert s41 EVAPORATIVECOOLINGDEVICEFORA CENTRIFUGE ROTARY SEAL 3 Clilmsi 2 Drawing 8 l at v 1.

s2 U.S.Cl 233/1 A, 62/119, 62/259, 74/18, 233/11, 277/22 [51] lnt.Cl. 13M 21/26, ABSTRACT; A device f cooling 3 rubbing seal i t f B04b 15/02 between a stationary and a rotating surface. The device in- [50] Field of Search 233/ 1 1,21, cludes a i ll l d led container having ther- 12, 1 A; 62/502, 514, 119.259; 74/ 18; 277/22, 74 mally conductive walls partially filled with a volatile liquid with a face portion forming the stationary surface. In opera- [56] References cited tion the heat generated at the interface causes the volatile UNITED STATES PATENTS liquid to evaporate and then condense by absorption of heat at 2 9 8 0 196 comelison er a1 62/119104 .s es weq eme wem .1

PATENIEI] M1831 I97! 3,602,425

WILLIAM L. SCHMIDT INVENTOR.

M i 38 ATTORNEYS EVAPORATIV E COOLING DEVICE FOR A CENTRIFUGE ROTARY SEAL BACKGROUND OF THE INVENTION Adequate cooling of high-speed rubbing seal interfaces may be quite difficult because of the extremely high heat generated in the small area of theinterface. Rotating seal interfaces are used'in such apparati as an ultracentrifuge similar to the one described in U.S. Pat. No. 3,103,489, the disclosure of which in incorporated herein by reference for continuously introducing and removing a liquid from the centrifuge chamber as it is rotated at high speeds. A liquid circulation system is employed to remove the heat produced at the seal interface. Since the interface is a small area, the circulating liquid may not absorb sufficient heat to cool the interface. If so, the heat of the interface may be transferred to the sample flowing past the interface. A typical biological sample could have its biological activity destroyed or impaired by the absorption of a substantial amount of heat generated at the interface of the rotating seal.

SUMMARY OF THE INVENTION AND OBJECTS According to the invention there is provided a cooling device for a rubbing seal interface subject to overheating. The device includes a sealed container partially filled with a volatile liquid. A thermally conductive lower wall of the container has a face forming at least a portion of the stationary surface which is in contact with a rotating surface at the rubbing seal interface. Heat generated at the interface is transferred through the lower wall to the liquid, causing the liquid to evaporate. To complete the closed-loop, heat transfer cycle, the formed vapor is condensed on the container walls by cooling means for the container walls, such asa liquid-cooling jacket in thermal contact with the container.

In a particularly preferred embodiment of the invention, the device is incorporated into an ultracentrifuge employing a rotating seal interface. A lower wall of the device forms at least a portion of the stationary surface in contact with the surface secured for rotation with the rotor.

It is an object of the invention to provide an improved device for cooling a rubbing seal interface.

It is a further object of the invention to provide a cooling device for a rubbing seal interface that significantly increases the amount of heat removal from the interface compared to prior art devices.

It is a further object of the invention to provide a cooling device for an ultracentrifuge, having a rotating seal interface, particularly adapted to be inserted at the interface of the rotating seal.

These and other object of the invention will become more clearly apparent from the following description when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view, partly in section, illustrating a centrifuge apparatus incorporating the cooling device of the invention;

FIG. 2 is an enlarged sectional view of the rotating seal delineated by the line 2-2 of FIG. 1 incorporating the cooling device of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cooling device of the invention will be described with respect to cooling the rotating seal interface of the type shown and described in U.S. Pat. No. 3,103,489. It is understood that the cooling device of the invention may be incorporated into any apparatus which includes a rubbing seal interface subject to overheating.

Referring to FIG. 1, the ultracentrifuge apparatus includes an outer housing 11 which serves to enclose the working parts. Housing 11 includes an upper wall 12 which is provided with an opening 13 through which a rotor 14 may be inserted into a rotor chamber 16. The chamber 16 is formedby a portion of the wall 12, the cylindrical wall 17, and the bottom wall 18.

A bell-shaped housing or support 19 is suitable secured to the upper wall 12, as, for example, by means of bolts 20. The support 19 is adapted to house and support the rubbing seal assembly 21, to be fully described hereinafter. A plate 22, secured near the bottom of housing 19, receives vacuum seal assembly 15, fully described in U.S. Pat. No. 3,103,489.

The rotor 14 is carried on a spindle 23, preferably made of flexible material to accommodate flutter of the rotor. Spindle 23 extends downwardly through a seal 24 formed in the bottom wall 18. Its lower end is joumaled in an oil-filled bearing 26. The bearing 26 is supported from the bottom wall 18 by downwardly extending spaced brackets 27. A driven pulley 28 is carried by the spindle. A variable speed drive motor 29 is provided for driving the belt 31 which engages the drive pulley 32 and the driven pulley 28 to impart a rotative force to the spindle. The motor 29 may be mounted to the bottom wall 18 by means of bracket 33.

A pair of inner and outer concentric tubes 36 and 37 extend downwardly and communicate with the interior of the rotor 14. Suitable rotor interiors are described in U.S. Pat. No. 3,103,489. The tubes form axial and annular fluid passages 38 and 39, respectively. The concentric tubes 36 and 37 rotate with the rotor and extend upwardly through a vacuum seal assembly 15 into a rotary rubbing seal 21. During a separation, sample fluid flows down passage 39 and through seal assembly 15 and into rotor 14. The fluid is subjected to centrifugal forces. The pressure causes the supemate to flow upward into passage 38 and to rubbing seal 21.

The rubbing or rotating seal includes a stationary seal member 41 and a rotating seal member 42. The rotating member 42 is carried within the cup-shaped housing 43 secured to the upper end of the outer tube 37. An O-ring 44 is disposed in the annular groove 45 and is adapted to provide a seal between the upper end of the tube 37 and the surroundings. The passages 46 and 47, formed in member 42 communicate with axial and annular passages 38 and 39, respectively. The inner tube 36 extends upwardly into the member 42 and is suitably sealed, as by packing 35.

The stationary seal member 41, which also functions as a cooling device, includes a top wall 49 which is provided with an opening 50 through which concentric inner and outer tubes 51 and 52, defining axial and annular passages 56 and 57, may be inserted. Member 41 also includes an outer cylindrical wall 53, which may be integral with wall 49, and a bottom wall 54. Wall 54 may include an annular flange 58, which cooperates with the flat portion of wall 49 to form a seat for tube 52. Tube 52 may be suitably sealed with wall 54 as by welding flange 58 to tube 52, and with wall 49, as by welding therebetween. Passage 57 communicates with annular opening 59 in wall 54. Opening 55 communicates with passage 47 and is sealed therewith by the rotating seal interface. Passage 56 communicates with passage 46 and is sealed therewith by the rotating seal interface.

An annular chamber 59 is defined by walls 49, 53 and 54, flange 58 and a portion of tube 52. An opening 60 may be provided in top wall 49 to accommodate the partial filling of chamber 59 with volatile fluid 61. After filling, the chamber 59 may be hermetically sealed by the insertion of a plug 62, such as an aluminum pop rivet. If refilling of the chamber is desired, the rivet may be drilled out and replaced after refilling. The fluid 61 may be any volatile refrigerant, such as Freon 21, liquid hydrogen, or liquid sodium, that boils at a temperature for cooling the interface to a suitable temperature for the particular sample flowing through the centrifuge. The walls 49, 53 and 54 are made of a thermally conductive material, such as copper, to provide efficient cooling of the interface, as will be explained hereinafter.

The upper end of passage 57 communicates with an annular groove 63 defined by tube 52 and cooperating plug 64 received by the cup-shaped portion of member 41 and retained therein by O-ring 69. Tubes 51 and 52 are suitably retained in and sealed with plug 64 as by O-rings 75. Plug 64 includes a passage 65 communicating at one end with groove 63 and at the other end with inlet passage 66. Plug 64 also includes a passage 80 communicating at one end with passage 56 and the other end with outlet passage 67.

Member 41 is received within housing 68 and retained therein by the O-ring 70. The upper end of the housing is threadably received by a guide 71 which, in turn, is slidably received in the collar 72.

The collar 72 threadably receives an end plug 73. A spring 74 is disposed between the end plug and the plug 64 and serves to urge the plug 64 and associated seal member 41 downwardly into pressure contact into the upper face of the member 42. Thus, a pressure face rotating seal is formed between the faces of the seal members 41 and 42. The seal is maintained under predetermined adjustable pressure by spring 74.

The space between the housing 68 and the stationary member 41 defines a cooling jacket 78 which communicates with fluid inlets and outlets 76 and 77. Suitable cooling liquid such as cooled water, may be circulated in the jacket 78 to cool the walls of member 41.

The jacket 78 and member 41 cooperate to produce a cooling device 79 for seal assembly 21. In operation of the centrifuge, sample flows from inlet passage 66 to the rotating seal interface and then into the rotor chamber. The supernate is centrifugally forced out of the rotor chamber past the rotating seal interface and through outlet passage 67. During operation, rotating member 42 rubs against stationary member 41 generating a frictional heat. This heat is transferred through thermally conductive bottom wall 54 to fluid 61 causing the fluid to boil and then evaporate, thus converting the frictional heat into heat of vaporization. The resulting vapors are then cooled and caused to condense on the inside of cooled thermally conductive walls 49 and 53. The walls are cooled by the circulation of a refrigerated liquid in jacket 78. Thus a closed loop heat transfer cycle is established in which the high coeffb cients of boiling heat transfer are utilized to absorb a large heat flux from the small area of the seal 21, while the larger area of chamber 59 is available for removal of the heat by forced convection. Thus the sample flowing past seal assembly 21 may be maintained at a constant cold temperature substantially regulated by the temperature of the fluid in the cooling jacket 78.

lclaim:

l. in an ultracentrifuge apparatus including a rotor, a rotary member secured for rotation with the rotor having tubes for supplying liquid to the interior of said rotor and removing liquid therefrom and a stationary member including liquid supply and removal passages respectively communicating with said tubes at a rotating seal interface formed between a face of the stationary member and a face of the rotary member, the improvement comprising: a cooling device for the rotating seal interface including a hermetically sealed container having thermally conductive lower, side, and upper wall portions, said lower wall portion forming a major portion of the stationary face of the rotary seal interface, a volatile liquid disposed in and partially filling said container, said liquid being in thermal contact with said lower wall portion and means for cooling the upper and sidewall portions of said con tainer, whereby heat generated at said face causes the volatile liquid to evaporate with the resulting vapor being caused to condense by heat absorbed from the vapor at the cooled container walls in a closed loop, regenerative heat transfer cycle.

2. In a rotating seal assembly including a stationary seal member, a rotating seal member, and means for urging the stationary and rotating seal members into sealing engagement to form a rotating sealing interface between the two engaging faces of the sealing members, the improvement comprising:

a closed container carried by one of said sealing members, said container fabricated of thermal conductive material and having upper, lower, and sidewalls, said lower wall forming a portion of the sealing engaging face of said sealing member, a volatile liquid disposed in said container with the liquid being in contact with the lower wall of said container, a cooling jacket surrounding the upper and sidewalls of said container, and means for circulating a cooling liquid through said cooling jacket whereby heat generated at said rotating seal interface is transferred through said lower wall of said container to said liquid causing the liquid to evaporate with the resulting vapor being caused to condense by heat absorbed from the vapor at the cooled container walls in a closed-loop heat transfer cycle.

3. The improvement as defined in claim 2 wherein said closed container is carried by said stationary seal member. 

1. In an ultracentrifuge apparatus including a rotor, a rotary member secured for rotation with the rotor having tubes for supplying liquid to the interior of said rotor and removing liquid therefrom and a stationary member including liquid supply and removal passages respectively communicating with said tubes at a rotating seal interface formed between a face of the stationary member and a face of the rotary member, the improvement comprising: a cooling device for the rotating seal interface including a hermetically sealed container having thermally conductive lower, side, and upper wall portions, said lower wall portion forming a major portion of the stationary face of the rotary seal interface, a volatile liquid disposed in and partially filling said container, said liquid being in thermal contact with said lower wall portion and means for cooling the upper and sidewall portions of said container, whereby heat generated at said face causes the volatile liquid to evaporate with the resulting vapor being caused to condense by heat absorbed from the vapor at the cooled container walls in a closed loop, regenerative heat transfer cycle.
 2. In a rotating seal assembly including a stationary seal member, a rotating seal member, and means for urging the stationary and rotating seal members into sealing engagement to form a rotating sealing interface between the two engaging faces of the sealing members, the improvement comprising: a closed container carried by one of said sealing members, said container fabricated of thermal conductive material and having upper, lower, and sidewalls, said lower wall forming a portion of the sealing engaging face of said sealing member, a volatile liquid disposed in said container with the liquid being in contact with the lower wall of said container, a cooling jacket surrounding the upper and sidewalls of said container, and means for circulating a cooling liquid through said cooling jacket whereby heat generated at said rotating seal interface is transferred through said lower wall of said container to said liquid causing the liquid to evaporate with the resulting vapor being caused to condense by heat absorbed from the vapor at the cooled container walls in a closed-loop heat transfer cycle.
 3. The improvement as defined in claim 2 wherein said closed container is carried by said stationary seal member. 